#include<bits/stdc++.h>
using namespace std;
#define rep(i,a,b) for(int i=a;i<b;i++)




int N, A[101010];
//-----------------------------------------------------------------------------------
int sol(int f) {
    int a = A[0];

    rep(i, 0, N - 1) {
        int t = f % 4;
        f /= 4;

        if (A[i + 1] == 0 && t == 3) return -1;

        if (t == 0) a += A[i + 1];
        if (t == 1) a -= A[i + 1];
        if (t == 2) a *= A[i + 1];
        if (t == 3) a /= A[i + 1];
    }

    return a;
}
//-----------------------------------------------------------------------------------
int main() {
    cin >> N;
    rep(i, 0, N) scanf("%d", &A[i]);

    int ans = 0;
    rep(flag, 0, 1 << ((N - 1) * 2)) ans = max(ans, sol(flag));
    printf("%d\n", ans);
}